Magnetoelastic coupling inRTiO3(R=La,Nd

Abstract

A detailed analysis of the crystal structure in RETiO3 with RE = La, Nd, Sm, Gd, and Y reveals an intrinsic coupling between orbital degrees of freedom and the lattice which cannot be fully attributed to the structural deformation arising from bond-length mismatch. The TiO6 octahedra in this series are all irregular with the shape of the distortion depending on the RE ionic radius. These octahedron distortions vary more strongly with temperature than the tilt and rotation angles. Around the Ti magnetic ordering all compounds exhibit strong anomalies in the thermal-expansion coefficients, these anomalies exhibit opposite signs for the antiferromagnetic and ferromagnetic compounds. Furthermore the strongest effects are observed in the materials close to the magnetic cross-over from antiferromagnetic to ferromagnetic order.

Symmetry Lowering in Extreme-Electron-Density Perovskite Quantum Wells

“…In bulk RTiO 3 , A-site displacements are correlated with tilts of the TiO 6 octahedra. The deviation angle in the 2 SrO well ($ 6 ) is significantly smaller than that of any RTiO 3 (ranging from 10.5 to 16.9 in LaTiO 3 and YTiO 3 , respectively) [17]. Using empirical relationships between A-site cation displacements along ½110 o and Ti-O-Ti bond angles in the RTiO 3 series [17], and interpolation to the cubic structure (0 deviation angle, 180 Ti-O-Ti angle), yields a Ti-O-Ti bond angle of $160 AE 5 for the 2 SrO layer quantum well.…”

“…GdTiO 3 is an orthorhombic distorted perovskite (space group Pnma [17]) with a þ b À b À tilt in Glazer notation [18]. A feature of this tilt system is the 2 degrees of freedom of the A-site (along x and z in Pnma), allowing it to shift to a more favorable position to optimize its local oxygen coordination [19,20].…”

Strong magnetoelastic coupling at the transition from harmonic to anharmonic order inNaFe(WO4)2with3d5Simon1, Ackermann2, Chapon3 et al. 2016Phys. Rev. BSelf Cite134220View full textAdd to dashboardCite

“…In contrast, the onset of incommensurate harmonic order at T N has no magnetoelastic impact on the b lattice parameter. In most magnetoelastic materials [26][27][28][29][30] , anomalies in the strain are coupled to the order parameter, typically the (staggered) magnetic moment, and thus appear just at T N , while the situation in NaFe(WO 4 ) 2 is more complex. In NaFe(WO 4 ) 2 , the change in the lattice is not proportional to a power of the averaged ordered moment, |m| , but to the emergence of anharmonicity either in the incommensurate phase or in the commensurate order.…”

“…Firstly, the effects are rather large yielding a relative reduction of the b lattice param- eter by up to ∆b b −2.6 · 10 −4 , and, secondly, there is no magnetoelastic anomaly at the onset of magnetic ordering in zero field, which results in the incommensurate phase. In most systems with strong magnetoelastic effects one may couple the strain, , with some power of the ordered moment defined as m av = |m| [26][27][28][29][30]40 , but in NaFe(WO 4 ) 2 the intermediate incommensurate phase renders the analysis more complex. Apparently there is only a weak coupling to the incommensurate phase, while that to the commensurate order parameter is strong.…”

Seebeck coefficient of a quantum confined, high-electron-density electron gas in SrTiO3

“…16)]. More severely nonstoichiometric GdTiO 3 films would become metallic 17 and show a reduced Curie temperature, 18 neither of which was observed for the films investigated here (see Refs. 12 and 13).…”